COMPOSITE FERMIONS CLOSE TO THE ONE-HALF FILLING OF THE LOWEST LANDAU LEVEL REVISITED

Abstract

By strictly adhering to the microscopic theory of composite fermions (CFs) for the Landau-level filling fractions ν e =p/(2p+1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by Willett and co-workers concerning two-dimensional electron systems with ν e close to ½. Our results imply that the electron band mass m b , as distinct from the CF mass m⋆, must undergo a substantial increase under the conditions corresponding to ν e ≈ ½. In view of the relatively low aerial electronic densities n e to which the underlying SAW experiments correspond, our finding conforms with the experimental results by Shashkin et al. [Phys. Rev. B 66, 073303 (2002)], concerning two-dimensional electrons in silicon, that signal sharp increase in m b for n e decreasing below approximately 2×1011 cm -2. We further establish that a finite mean-free path ℓ0 is essential for the observed linearity of the longitudinal conductivity σxx(q) as deduced from the SAW velocity shifts.